Scientists divide cetacean species into two groups, depending on whether they have teeth or not.

Toothed whales (Odontocetes)

The name ‘toothed whales’ can be a little misleading, because dolphins and porpoises also belong to this group. It does not only describe the big creatures that come to your mind when you think of whales, but also their smaller relatives. The most important trait of toothed whales is what gives them their name: they have teeth. This is the easiest difference to spot between baleen and toothed whales.
In almost all toothed whale species, their teeth are cone-shaped and not used for chewing (the exception are Amazon River dolphins; they have two different types of teeth in their mouths). They hunt and catch one prey animal at a time, such as fish, squid, seals, sea lions and even birds. Their prey is then swallowed whole, if it is not too big, or bitten into pieces small enough to swallow. Some toothed whales barely have any teeth because they feed only on squid, which they simply suck into their mouths.

Narwhals tusking with each other
© Glenn Williams/Wikimedia Commons

The male narwhal has a long tusk protruding from its upper jaw. The tusk is actually a modified tooth. There is much debate about what narwhals use their tusks for, but it may be used in competition for females and it can grow to 2-3m long and weigh up to 10kg.

Toothed whales are able to echolocate, which they use to hunt and swim in dark waters. Echolocation is a very precise way of sensing the environment. The animal sends out a stream of sounds (such as the dolphins’ “clicks”), which bounce off any objects nearby and return through the water. From the sounds received, the animal can tell the size, position and distance of an object. Dolphins can even tell the difference between different objects (a dolphin can tell the difference between a table tennis ball and a golf ball because of their different densities) and “see” the surface of things. Toothed whales are specialized for hunting agile prey like fish even though they might not be able to see them.

Toothed whales range greatly in size. The smallest are the Vaquita and Hector’s dolphins. The vaquita lives in the Gulf of California and reaches sizes of 1.2-1.5m (4-5ft). It is highly endangered, and there are only about 100-300 of them left in the world. Hector’s dolphins live only in New Zealand and measure about 1.4m, they are also endangered, especially their relatives the Maui’s dolphins, of which there are only 80 animals left. The biggest Odontocete is the Sperm Whale, which can reach almost 20m in length (65ft).

The Dall’s porpoise is one of the fastest of all the toothed whales
© GregTheBusker/Wikimedia Commons

Toothed whales populate all oceans of the world, and some also live in rivers. Mostly they are social animals. Some dolphin species, including orcas, form close groups or pods that can get as big as 1000 animals. Toothed whales are also rapid swimmers. Dall’s Porpoises and orcas are both incredibly fast, reaching speeds of 55kph-56kph


Do you want to learn more about toothed whales? Check out our Species Guide!


Baleen whales (Mysticetes)

This group of whales has the scientific name Mysticetes. The word comes from the Greek word meaning moustache, because the inner edge of the baleen looks like a moustache. These whales don’t have any teeth but instead they have baleen (which is also known as “whalebone”). Baleen is made of keratin, like our fingernails and hair. It continues to grow as long as the whale lives, because it wears down at its tips so it needs to be replaced. The color of baleen ranges from black to yellow or white, depending on the species of whale. Bowhead whales have the longest baleen; it can be up to 5m (16ft) long. Baleen acts like a sieve, filtering plankton or small fish out of the water so that the whale can eat them.

This is Antarctic Krill, eaten by a lot of whales
© Uwe Kils/Wikimedia Commons

Baleen whales are some of the largest of all the whale species; the smallest species (the pygmy right whale) still reaches 6m (19ft) long. With a length of around 30m (98ft), the blue whale is the biggest creature ever to have lived on this planet! As you can probably imagine, they need to eat plenty to survive—the equivalent of you eating 300 chocolate bars every day! But blue whales obviously don’t eat chocolate; they prefer a diet of krill (small shrimp-like creatures). They consume about 40 million krill every day—that’s about the weight of a female African elephant.

During feeding times, baleen whales can come together and sometimes cooperate to catch prey, but otherwise they are often found alone.
While all baleen whales filter their food out of the water, there use a number of different feeding techniques: there are skimmers, gulpers and suckers. 

The folds of skin that a humpback whale has on his throat allow his mouth to stretch amazingly wide, which means it can catch large amounts of prey all at the same time  © American Cetacean Society

The folds of skin that a humpback whale has on his throat allow his mouth to stretch amazingly wide, which means it can catch large amounts of prey all at the same time
© American Cetacean Society

During mating and feeding seasons some species briefly form groups; however, mothers and calves have a particularly close bond. Unlike many other mammals, female baleen whales are bigger than males, maybe because they have to care for their calves while migrating long distances. Whale pregnancies last for 10 to 16 months. They seldom have more than one baby at a time. When the calf is born, other females help to protect the mother and her calf.

These whales cooperate to feed © Wikimedia Commons

These whales cooperate to feed © Wikimedia Commons

A baleen whale baby has to keep up with his or her mother from the very first day of birth, but won’t leave her for about a year. The mother whale will nurse her baby with very fatty milk for about a year, as well as teaching it to feed and protecting it from predators. Still, a newborn blue whale doesn’t have to fear much: it already measures 7m (23ft) at birth and weighs 2,000kg—the weight of an average car.